I bought a used master cylinder off ebay. (wrong move) Dismantled all of the brake lines. replaced all copper washers. re assembled with new (used) MC. Tried to reverse bleed. No fluid would move. Cracked joints , fluid escaped. Cracked joint on master cylinder fluid escaped. Removed MC. added fluid, pumped and none came out. Dismantled MC. Blew air through -all orifices ok. cleaned piston assembly which was gunky in the grooves replaced it. Tried again, still no joy no fluid out or in. Gave up, don’t understand Replaced original MC to see if replacing all washers had made any difference. Reverse bled, all seemed to bleed fine. Squeezed lever - no pressure at all. Pumped gently and air bubbles came up in the reservoir as before. The lines are bled, no air comes out of base of MC when reverse bleeding. Pump the lever gently and air bubbles up.In desperation I have ordered a new master cylinder. Seriously hacked off!Something that is usually so simple is conspiring to drive me mad! AND bankrupt me.To top it all, a heavy shower soaked me and the bike!